1) Field of the Invention
The present invention relates to eliminating noise of a data bus circuit provided on a mother board.
2) Description of the Related Art
Mother boards of personal computer/advanced technology (PC/AT) compatible machines are typically provided with a 16-signal-line integrated drive electronics (IDE) data bus. This data bus is arranged on the mother board between a south bridge and a bay.
The south bridge includes a transmitting side device, which is a series of chip sets that administer data passing between a central processing unit (CPU), a random access memory (RAM), and an expansion card. On the other hand, the bay includes a loading side device, such as a compact-disc read only memory (CD-ROM) drive and a floppy disk drive. The data bus electrically connects the transmitting side device and the loading side device, to form a path that transmits and receives data. A related technology is disclosed in Japanese Patent Application Laid Open No. H3-235111.
The data bus functions as an antenna and generates high-frequency noise near the bay. There are regulations that prohibit generation of high-frequency noise that can cause electromagnetic coherency. Specifically, operation of the data bus must not inhibit operation of other devices, or cause electromagnetic interference (EMI) that exceeds a predetermined level of interference and affects the human body.
Lot of High-frequency noise is generated when the transmitting side device and the loading side device are driven by different power sources of different voltages. The leakage of EMI to the outside can be prevented by adhering a gasket or a conductive cloth to a conductive surface of a frame ground (FG) that covers the bay, so as to shield the high-frequency noise emitted from the bay side of the data bus.
However, this method requires additional components and processing steps, which leads to increased cost and weight of the machine.